Myocardial sympathetic innervation in the athlete's sinus bradycardia: Is there selective inferior myocardial wall denervation?

Montserrat Estorch, Ricard Serra-Grima, Albert Flotats, Carina Marí, Lluís Bernà, Ana Catafau, Joan Carles Martín, Ana Tembl, Jagat Narula, Ignasi Carrió

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Background. Sinus bradycardia in trained athletes is predominantly a manifestation of increased vagal tone, but it is not known whether an alteration in the cardiac sympathetic system can contribute to blunted chronotropic response. This study assessed the integrity of the sympathetic system in trained athletes with sinus bradycardia by means of the iodine-123-metaiodobenzylguanidine (123I-MIBG) procedure. Methods and Results. Fourteen athletes with sinus bradycardia and 8 athletes with a normal heart rate were explored by means of planar and single photon emission computed tomography MIBG studies. The heart/mediastinum ratio, regional myocardial distribution, and percent of regional myocardial MIBG uptake were evaluated. The heart/mediastinum ratio in athletes with sinus bradycardia was 1.87 ± 0.10, and in athletes with a normal heart rate, the heart/mediastinum ratio was 1.86 ± 0.16 (P = not significant). In athletes with sinus bradycardia, the regional distribution of MIBG showed an inferior and apical uptake defect in 8 athletes, an inferior, apical, and septal defect in 3 athletes, an inferior defect in 1 athlete, and normal distribution in 2 athletes (14%). In athletes with a normal heart rate, the regional distribution of MIBG showed an apical uptake defect in 3 athletes and normal distribution in 5 athletes (63%). The percent of regional MIBG uptake in the inferior region was significantly reduced in athletes with sinus bradycardia (44% ± 13% vs 72% ± 11%, P < .01). Conclusion. These results show severely reduced myocardial MIBG distribution in the inferior region in athletes with sinus bradycardia, suggesting selective inferior myocardial wall sympathetic denervation, which may be related to increased vagal tone.

Original languageEnglish
Pages (from-to)354-358
Number of pages5
JournalJournal of Nuclear Cardiology
Volume7
Issue number4
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • Athlete
  • Iodine-123-metaiodobenzylguanidine
  • Iodine-123-metaiodobenzylguanidine scintigraphy
  • Sinus bradycardia
  • Vagal tone

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